1. Field of the Invention
The present invention relates to an optimum defrosting cycle control method for an inverter refrigerator for obtaining an optimum defrosting cycle by accumulatively computing frosting time based on a frosted amount by operation cycles in an operation speed-variable inverter refrigerator. In particular, the present invention relates to an optimum defrosting cycle control method for an inverter refrigerator which is capable of obtaining an optimum defrosting cycle by providing different accumulative ratios based on an high-speed operation, mid-speed operation, and low-speed operation according to a frequency of a compressor by operation cycles, for thereby decreasing a power consumption of a refrigerator.
2. Description of the Background Art
In a refrigerator, a freezing system operates by a freezing cycle in which heat is absorbed from the interior of the refrigerator, and the thusly absorbed heat is radiated to the outside of the refrigerator in order to retain a lower temperature in the refrigerator than the surrounding outside temperature.
Generally, to absorb the heat in the refrigerator, the heat must be absorbed in a lower temperature than that of the interior of the refrigerator, and the above- described function is performed by an evaporator(cooling unit). To maintain the temperature in a conventional refrigerator lower than -18.degree. C., the temperature of the evaporator must be lower than -23.degree. C. Therefore, the temperature of the evaporator is the lowest in the refrigerator, and the moisture in the refrigerator is mostly frosted on the evaporator. When a certain amount of moisture is frosted on the evaporator, the efficiency of the evaporator decreases, thus the frosted moisture should be removed periodically.
In addition, the amount of moisture frosted on the evaporator is different according to the temperature and blowing capacity of the evaporator. The higher the temperature of the evaporator and the smaller the blowing capacity, the less amount of frost. Therefore, in the inverter refrigerator of the present invention, a defrosting cycle is set, considering that the frosted amount varies according to the evaporating temperature by operation frequencies with the variation of the operation speed of a compressor.
FIG. 1 is a schematic view of a conventional refrigerator. As shown therein, the conventional refrigerator comprises a compressor 13 providing a high temperature and high pressure gaseous coolant, an evaporator 11 which cools a freezing compartment 20 and a refrigerating compartment 30 through heat exchange with an environment division by evaporating the coolant which is provided from the compressor 13, by changing the coolant into a low temperature and low pressure liquid while passing through a condenser(not shown) and a capillary tube(not shown), a damper 12 which controls the temperature of the refrigerating compartment by supplying cold air from the freezing compartment 20 to the refrigerating compartment or cutting off the same, and a freezing fan motor 10 which drives a freezing fan which forcedly blows cold air as a process of a cold air circulation.
FIG. 2 is a block diagram of a defrosting circuit in a conventional refrigerator. As shown therein, the defrosting circuit comprises a micro computer 21 which outputs various kinds of control signals by each unit in order to control the temperature of the freezing and refrigerating compartments, a compressor COMP which compresses coolant required for cooling the freezing and refrigerating compartments, a L-cord heater 22 and TE-plate heater 23 for melting frost formed on the evaporator, first through third relays RY1-RY3 which controls the operation of the evaporator 11, L-cord heater 22, and TE-plate heater 23 under the control of the micro computer 21, and a freezing sensor S1 for detecting the temperature of the freezing compartment.
FIG. 3 is a chart showing an operation cycle with respect to an operation time of the compressor for obtaining accumulated defrosting time in FIG. 1.
Referring to FIGS. 1 through 3, the thusly constituted conventional art will be explained in detail as follows.
First, when source voltage is applied, the micro computer 21 turns the first relay RY1 "ON" through an output terminal P1 thereof. As the first relay RY1 is turned "ON", the compressor COMP operates to compress gaseous coolant with high temperature and high pressure, and supplies the compressed coolant to the evaporator 11 in FIG. 1 via the condenser(not shown) and capillary tube(not shown). Then, the evaporator 11 absorbs heat in the freezing compartment 20 by evaporating the coolant and radiates the heat to the outside of the freezing compartment 20, thereby cooling the freezing compartment 20.
Since the transfer path of the coolant is the same as the cooling cycle of a conventional refrigerator, the description thereof will be omitted.
The freezing compartment 20 is then cooled by driving the freezing fan motor 10 to forcedly blow cold air for cold air circulation. When cooling is thusly implemented, the micro computer 21 reads the temperature of the freezing compartment from the freezing sensor S1 attached in the freezing compartment 20. When the thusly read temperature of the freezing compartment reaches a predetermined temperature, the micro computer 21 turns the first relay RY1 "OFF" to thereby deactivate the compressor COMP.
The temperature in the refrigerating compartment is controlled by the operation of supplying the cold air of the freezing compartment to the refrigerating compartment or cutting off the same by turning a damper 12 "ON" or "OFF" for controlling the cold air of the refrigerating compartment 30.
When the above-described operation is implemented, the micro computer 21 accumulatively computes the operation time of the compressor COMP When the thusly accumulated time reaches a certain amount of time(e.g. 7 hours approximately), the micro computer 21 drives the second and third relays RY2 and RY3 for defrosting operation. That is, as shown in FIG. 3, each operation time of the compressor T1, T2, T3, T4, and T5 is all computed accumulatively to thereby obtain the accumulated defrosting time T. EQU T=T1+T2+T3+T4+T5
When the thusly obtained time reaches 7 hours, the micro computer 21 turns the second and third relays RY2 and RY3 "ON" through output terminals P2 and P3 thereof. With the second and third relays RY2 and RY3 turned "ON", the L-cord heater 22 and TE-plate heater 23 are activated.
Then, the L-cord heater 22 and TE-plate heater 23 are operated to melt frost (or ice) formed on the evaporator 11. When the operation of melting the frost formed on the evaporator 11 is carried out, the micro computer 21 reads the temperature from a defrosting sensor S2. When the temperature read from the defrosting sensor S2 reaches a certain degree, the second and third relay RY2 and RY3 is turned "OFF" to stop the operation of the heaters.
By the above-described process, the operation of the refrigerator and the defrosting operation are repeated.
However, in the conventional art described above, a defrosting operation is automatically carried out when the accumulated time reaches a certain amount of time(e.g. 7 hours) by accumulatively computing the operation time of the compressor so that the operation speed of the compressor may be the same all the time, that is, a defrosted amount per unit time may be almost constant. Therefore, it is not relevant to implement an automated defrosting operation when the operation speed of the compressor is variable like an inverter refrigerator. For example, an over defrosting operation is performed and a power consumption is increased since the defrosting operation performed at an accumulative time in a state that a certain frosted amount is not obtained for an effective defrosting operation due to an increase operation factor in a case that a low speed operation of the compressor is continued. As a result, an excessive defrosting is done, thereby increasing a power consumption.